A tire serves to withstand the load of automobiles, to reduce impact with a road surface, and to transfer a driving force or braking force of an automobile to the ground.
In general, the tire refers to a complex of fiber/steel/rubber and normally has a structure as shown in FIG. 1.
Tread (1): a portion that is in contact with the road surface. It should afford frictional force required for driving and braking, have good wear resistance, withstand external impact, and have minimal heat generation.
Body ply (or carcass) (6): a cord layer inside the tire. It should support a load, withstand impact, and have strong fatigue resistance to bending and stretching while the vehicle is running.
Belt (5): located between the body plies. It consists of steel wire in most cases, reduces external impact, and maintains a large area of contact of the ground to the surface of the tread to afford excellent vehicle running stability.
Side wall (3): a rubber layer between a part below a shoulder (2) and a bead (9). It serves to protect the inner body ply (6).
Inner liner (7): located inside the tire instead of a tube. It prevents air leakage to enable a pneumatic tire.
Bead 9: square or hexagonal wire bundle formed of rubber-coated steel wire. It serves to stabilize and fix the tire in a rim.
Cap ply (4): a special cord located on a belt of a radial tire for some passenger cars. It minimizes movement of the belt during automobile running.
Apex (8): triangular rubber filler used to minimize dispersion of the bead, reduce external impact to protect the bead, and prevent air inflow during molding.
Recently, a tubeless tire in which high pressure air of about 30˜40 psi is injected without using a tube has become widely been used. In order to prevent inside air from leaking outside during automobile running, an inner liner having a high gas barrier property is disposed in an inner layer of the carcass.
Previously, a tire inner liner consisting mainly of rubber components such as butyl rubber or halobutyl rubber having relatively low air permeability was used, but in order to achieve a sufficient gas barrier property of the inner liner, the content of the rubber components and the thickness of the inner liner should be increased.
As the content of the rubber components and the thickness of the tire are increased, the total weight of the tire is increased, the fuel efficiency of automobiles may be lowered, air pockets may be generated between rubber in the inner surface of a carcass layer and an inner liner, or the shape or physical properties of the inner liner may be changed in a tire vulcanizing process or in an automobile running process.
Accordingly, various methods have been suggested to decrease the thickness and weight of the inner liner to increase fuel efficiency, reduce changes in the shape or physical properties of the liner in a tire vulcanizing process or an automobile running process, and the like.
However, previously known methods have limitations in maintaining excellent air permeability and tire moldability while sufficiently reducing the thickness and weight of the inner liner. In addition, there were problems in that these methods use an additional rubber type of tie gum in order to rigidly bond a carcass layer in the inside of a tire and thus weight of the tire is increased and fuel efficiency of automobiles is lowered.
Further, the inner liner manufactured by the previously known methods had cracks generated and did not have sufficient fatigue resistance due to repeated deformations in the tire manufacturing process or in an automobile running process.
Accordingly, there is a need to develop a tire inner liner that can be easily coupled to a tire inner part while having a relatively thin thickness so that weight of the tire can be reduced, and that can not only endow physical properties such as an excellent gas barrier property and moldability but also have sufficient fatigue resistance which can withstand repeated deformations.